How Is Atrial Fibrillation Diagnosed?

Atrial fibrillation (AFib) is an abnormal heart rhythm ( arrhythmia) that may or may not cause symptoms. Sometimes a doctor spots it when checking for something else during a physical exam or test. Other times, symptoms lead the doctor to suspect AFib.

You may need a variety of tests to confirm a diagnosis of AFib and to find out what's causing it and the best way to treat it. Sometimes a primary care doctor, such as a family practitioner or internist, diagnoses AFib. But in many cases, you see a doctor who specializes in diagnosing and treating heart conditions (a cardiologist). Cardiologists with a specialty in arrhythmias are called electrophysiologists.

In addition to tests, the doctor checks your medical and family history. This includes detailed questions about your symptoms, health habits, and health problems you or another family member have had.

Electrocardiogram (ECG or EKG)

An ECG is the most helpful test for diagnosing AFib. It's a simple, painless test that records your heart's electrical activity. It can show the:

Speed of your heartbeat

Rhythm of your heartbeat

Strength and timing of electrical signals passing through different parts of the heart

A health care professional places small patches, called electrodes, on different areas of your body, including several on your chest. The electrodes pick up signals and create waves on the ECG. Each shows how long it takes for impulses to travel through different parts of the heart. It allows the doctor to trace your heart's overall electrical activity.

Because it is so brief, a standard ECG won't always catch AFib. Sometimes you need to a portable ECG monitor to keep tabs on your heart over a longer period. Holter or event monitors can do this.

Holter monitors. You keep a Holter monitor with you for 24 to 48 hours to continuously record your heart's electrical activity. This increases the chances of picking up an abnormal heart rhythm.